Android-->Behavior上手入门

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开始布局时,方法回调顺序:

1:StickBehavior([context, attrs])-> 2:onAttachedToLayoutParams([params])->3:layoutDependsOn([parent,child,dependency])->//当dependency是你需要监听的View时,需要返回true, 否则dependency View位置改变, 或者大小改变不会有onDependentViewChanged回调.4:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->5:layoutDependsOn([parent,child,dependency])->6:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->7:layoutDependsOn([parent,child,dependency])->8:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->9:layoutDependsOn([parent,child,dependency])->10:onMeasureChild([parent,child,parentWidthMeasureSpec,widthUsed,parentHeightMeasureSpec,heightUsed])->11:onLayoutChild([parent,child,layoutDirection])->12:onDependentViewChanged([parent, child, dependency])-> //当layoutDependsOn返回true时, 才会有这个回调

开始滚动子View时, 方法回调顺序

1:onStartNestedScroll([coordinatorLayout, child, directTargetChild, target, nestedScrollAxes])-> //此方法必须返回true, 否则之后的滚动事件将没有回调2:onNestedScrollAccepted([coordinatorLayout, child, directTargetChild, target, nestedScrollAxes])->3:onNestedPreScroll([coordinatorLayout, child, target, dx, dy, consumed])-> 4:onNestedScroll([coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed])-> //当快速滑动的时候, 才会触发fling回调//4.1:onNestedPreFling([coordinatorLayout, child, target, velocityX, velocityY])-> //4.2:onNestedFling([coordinatorLayout, child, target, velocityX, velocityY, consumed])-> 5:onStopNestedScroll([coordinatorLayout, child, target])->

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源码地址:
https://github.com/angcyo/uiview/blob/master/RLibrary/uiview/src/main/java/com/angcyo/uiview/design/StickBehavior.java

public class StickBehavior<V extends View> extends CoordinatorLayout.Behavior<V> {    View mTargetView;    /**     * 悬停区域的高度 px     */    int stickHeight = 0;    /**     * 为了保存已经偏移的距离     */    int lastTop = 0;    public StickBehavior() {    }    public StickBehavior(Context context, AttributeSet attrs) {        super(context, attrs);    }    /**     * 当CoordinatorLayout在layout的时候, 会回调此方法, 告诉你,     * 是否需要得到dependency View的位置大小改变的监听,如果你需要, 那么必须返回true     */    @Override    public boolean layoutDependsOn(CoordinatorLayout parent, V child, View dependency) {        if (mTargetView == null) {            lastTop = 0;        }        if (dependency instanceof StickLayout) {            //StickLayout只是用来判断是否是目标的标识, 没有任何不同支持,            //你也可以通过getId判断id是否相等, 来处理            mTargetView = dependency;            stickHeight = (int) (40 * child.getContext().getResources().getDisplayMetrics().density);            return true;        }        return super.layoutDependsOn(parent, child, dependency);    }    /**     * 只有当layoutDependsOn返回true时, 才会回调.     * 当dependency对应的View, 发生了改变, 就会回调此方法.     * 你可以在此更新child的位置     */    @Override    public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) {        lastTop = dependency.getTop();        child.setTop(dependency.getBottom());        return true;    }    /**     * 测量child的大小, 和自定义view的套路一样     */    @Override    public boolean onMeasureChild(CoordinatorLayout parent, V child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {        child.measure(View.MeasureSpec.makeMeasureSpec(parent.getMeasuredWidth(), View.MeasureSpec.EXACTLY),                View.MeasureSpec.makeMeasureSpec(parent.getMeasuredHeight() - stickHeight, View.MeasureSpec.EXACTLY));        return true;    }    /**     * 布局child的位置, 和自定义view的套路一样     */    @Override    public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {        if (mTargetView != null) {            ViewCompat.offsetTopAndBottom(mTargetView, lastTop);            int top = mTargetView.getBottom();// - Math.abs(lastTop);            child.layout(0, top, child.getMeasuredWidth(), top + child.getMeasuredHeight());            return true;        }        return super.onLayoutChild(parent, child, layoutDirection);    }    /**     * 必须返回true, 否则你收不到子View滚动的事件     */    @Override    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) {        return true;    }    /**     * 当子View开始滚动之前, 你可以通过此方法消耗掉滚动事件, 并偏移child的位置     */    @Override    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed) {        if (dy == 0 || (dy < 0 && ViewCompat.canScrollVertically(target, -1))) {            return;        }        int offsetMax = mTargetView.getMeasuredHeight() - stickHeight;        int top = mTargetView.getTop();        int offset = 0;        if (dy > 0) {            //上滑            offset = Math.min(dy, offsetMax + top);        } else if (dy < 0) {            //下滑            offset = Math.max(dy, top);        }        ViewCompat.offsetTopAndBottom(mTargetView, -offset);        consumed[1] = offset;    }    /**     * 用来处理快速滑动     */    @Override    public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY) {        L.e("call: onNestedPreFling([coordinatorLayout, child, target, velocityX, velocityY])-> ");        if (velocityY < 0 && ViewCompat.canScrollVertically(target, -1)) {            return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);        }        int offsetMax = mTargetView.getMeasuredHeight() - stickHeight;        if (velocityY > offsetMax) {            mTargetView.setTop(-offsetMax);            //mTargetView.setBottom(mTargetView.getMeasuredHeight() - offsetMax);            animToBottom(mTargetView.getMeasuredHeight() - offsetMax);        } else if (velocityY < -offsetMax) {            mTargetView.setTop(0);            //mTargetView.setBottom(mTargetView.getMeasuredHeight());            animToBottom(mTargetView.getMeasuredHeight());        }        return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);    }    void animToBottom(int bottom) {        ValueAnimator animator = ObjectAnimator.ofInt(mTargetView.getBottom(), bottom);        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator animation) {                mTargetView.setBottom((Integer) animation.getAnimatedValue());            }        });        animator.setInterpolator(new LinearInterpolator());        animator.setDuration(100);        animator.start();    }}

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